1. Field of the Invention
The present invention relates to image processing apparatuses, image processing methods, recording media, and programs, and, more particularly, to an image processing apparatus and image processing method capable of easily and accurately detecting ridge strength of an image, a recording medium, and a program.
2. Description of the Related Art
A new television broadcasting standard such as the HDTV (High Definition Television) standard enabling high-definition broadcasting is currently becoming increasingly popular in addition to the known NTSC (National Television Standards Committee) and PAL (Phase Alternation by Line) standards. Furthermore, electric home appliances such as digital still cameras using digital image data are becoming increasingly widespread. Thus, image data resolutions used by users are becoming diversified.
On the other hand, in Flat Panel Displays (FPDs) that are image display devices currently in widespread use, the number of pixels used is fixed regardless of whether the display system thereof is a plasma display system or a liquid crystal display system. Accordingly, if the displayable resolution of a display device does not match the resolution of image data, the resolution of the image data is required to be converted into the displayable resolution of the display device. This resolution conversion is achieved by horizontally and vertically performing one-dimensional interpolation processing upon original image data using pixels included in the image data.
As image interpolation methods, for example, there are the nearest neighbor interpolation method (see, for example, Japanese Unexamined Patent Application Publication No. 09-50516) in which a pixel is interpolated at an interpolation position using the value of a pixel nearest to the interpolation position included in original image data, the bilinear interpolation method (see, for example, Japanese Unexamined Patent Application Publication No. 09-50516) in which a pixel is interpolated at an interpolation position using a weighted average of pixel values of two pixels adjacent to the interpolation position, the bicubic interpolation method (see, for example, Japanese Unexamined Patent Application Publication No. 2001-216124) in which a pixel is interpolated at an interpolation position using a weighted average of pixel values of four pixels near the interpolation position, the diagonal interpolation method (see, for example, Japanese Unexamined Patent Application Publication No. 2004-153668) in which the direction of an edge included in an image is detected, and a pixel is interpolated at an interpolation position using pixels on the both sides of the interpolation position in the edge direction, and an interpolation method (hereinafter, referred to also as a high-order filter interpolation method) in which the number of taps and the order of an interpolation filter (filter factor) are increased, and image interpolation is performed using an interpolation filter having characteristics close to ideal filter characteristics (sinc function).